Magnetic variable-speed device



P 29, 1959 E. COHEN ETAL 2,906,900

MAGNETIC VARIABLE-SPEED DEVICE Filed Dec. 2, 1957 INVENTORS:

ELIE COHEN 2 By SZYMON WAGE/VT United States Patent MAGNETIC VARIABLE-SPEED DEVICE Elie Cohen and Szymon Roth, Paris, France Application December 2, 1957, Serial No. 700,128

Claims priority, application France April 23, 1957 4 Claims. (Cl. 310-101) This invention relates to magnetic variable-speed drive devices or speed variators, more particularly to speed variators operating on the eddy-current principle as disclosed inter alia in our co-pending US. application Ser. No. 489,642, flled February 21, 1955, now Pat. No. 2,847,594, issued August 12, 1958, and also in our earlier French patents Nos. 1,117,613 and 1,132,712.

In prior magnetic variable-speed devices of the contemplated type there was no provision for reversal of the drive, since the secondary or driven element of the drive was rotated always in a constant direction regardless of the polarity of the current flowing through the excitation windings. In those applications of the device where reversible drive is a requisite, it was therefore necessary to provide a reversible drive motor and reverse the sense of motor operation every time the sense of operation of the output element had to be changed. This is a serious drawback especially in connection with high driven loads.

It is a principal object of this invention to provide an improved magnetic variable-speed device or speed variator which will be reversible in operation. Another object is to provide a variable drive device of the specified type wherein the direction of rotation of the output or driven element of the device may be instantly reversed by throwing a circuit switch. A further object is to provide such a magnetic drive device embodying improved retarding or brake means of high eiflciency, and one that will be capable of efficiently and steadily controlling a relatively high driven load even under conditions of zero or approximately zero output velocity. Broad objects lie in the provision of improved magnetic variable-speed drives or speed variators eminently suitable for use with heavy equipment such as hoisting and handling apparatus as well as servomechanisms of all kinds, and/ or suitable for operation by remote control.

According to an important aspect of the invention, an improved variable-speed drive device comprises, in combination, a rotatable input element, a pair of independently rotatable driven elements coaxial therewith, a pair of magnetic means selectively energizable for establishing an eddy-current drive connection from said drive element to a desired one of said driven elements, a rotatable output element, and respective gear trains of different drive ratios connecting each driven element with the output element. According to a preferred feature of the invention, the said drive ratios are of opposite sign, whereby selective energization of one or the other of said magnetic means will cause the driven element to be totated in one or the opposite direction.

The above and further objects, aspects and features of the invention will appear as the disclosure proceeds, with reference to the accompanying drawing the sole figure of which is a simplified view, mainly in cross section, of one embodiment of our improved reversible magnetic variable-speed device. It will be understood that the drawing and related descriptive matter are given for the 2,906,900 Patented Sept. 29, 1959 ICC purpose of imparting a clear understanding of the invention but not for limiting the scope thereof.

As shown, a drive or input shaft 1 is supported for rotation in spaced bearings 3 and 4 mounted in any suitable frame or casing, not illustrated. An output shaft 2 is similarly supported in the frame in parallel spaced relation with the input shaft 1. Secured on a central portion of input shaft 1 substantially midway between the bearings 3 and 4 is an inner rotor 5 made of a suitable magnetic material, e.g. magnetic steel, and including as shown a hub part 7, a radially projecting flange 5 and an annular peripheral flange of substantial extent in the axial direction, said peripheral flange being externally formed with parallel axially extending ribs, grooves, or splines 6. Reference may be had to our aforementioned earlier patents for further description of a similar type of magnetic rotor.

Surrounding the input shaft 1 on each side of the rotor hub 7, between it and the respective bearing 3 or 4, are a pair of tubular shafts 8 and 9 respectively, which are journalled for free rotation around the shaft 1 through bearings 10 and 11, so that the tubular shafts 8 and 9 are freely rotatable independently both of each other and of the input shaft 1 around which they are mounted. Tubular shafts 8 and 9 constitute the hub parts of respective driven rotors or drag-cups generally designated 12' and 13', each of which comprises a radial flange or wall, secured to tubular hub 8 or 9, and an annular peripheral flange 12 or 13 both of which extend towards each other around the outer periphery of rotor 5 with the inner adjacent ends of said flanges 12 and 13 defining a comparatively narrow gap around the midplane of said rotor 5.

Surrounding the composite rotor and dual drag-cup structure just described is an annular stator 14 of magnetic steel or the like, in which a pair of axially spaced windings 15 and 16 are housed so that winding 15 surrounds drag-cup 12 while winding 16 surrounds drag-cup 13. The peripheral flange of each of drag-cups 12 and 13 is preferably formed with an annular groove in its outer surface, as indicated at 12a and 13a, so as to provide areas of increased magnetic reluctance substantially registering with the transverse midplane of each winding. With this arrangement, it will be seen that the excitation of winding 15 or of winding 16 will generate looped magnetic lines of force as respectively indicated by dotdash lines, with the magnetic flux loop in each magnetic circuit extending in the stator casing 14 around the respective winding 15 or 16, through the flange of dragcup 12 or 13, and into and out of the flange 5 of magnetic rotor 5, extending in the latter to a substantial depth beyond the peripheral splines 6 thereof. The provision of grooves 12a and 13a prevents shorting of the magnetic circuits through the flanges of driven rotors 12 and 13.

Secured on the outer ends of tubular shafts or hubs 8 and 9 are respective drive gears 17 and 18, and secured at spaced points on the output shaft 2 are respective driven gears 21 and 23. Gear 17 drives gear 21 by way of a gear train including two intermediate idler gears 19 and 2t suitably journalled in the frame of the device. Gear 18 drives gear 23 by way of a gear train including a single intermediate idler gear 22 similarly journalled in he frame. It will be noted that whereas the gear drive from rotor hub 8 to the driven shaft 2 includes an even number of gears the drive from rotor hub 9 to the driven shaft includes an odd number of gears; hence for a given direction of rotation of the rotor hubs 8 and 9 (say clockwise as viewed from the right-hand end of the drawing) the gear train 17192021 will tend to drive the shaft 2 in one direction (counterclockwise) whilst gear train r 3 18-22-23 will tend .to drive the shaft 2 in the opposite direction (clockwise). This condition may be conveniently expressed by saying that the two gear trains specified possess drive ratios of opposite sign. 7

It will further be seen that the apparatus described may be considered as actually comprising two cooperating eddy-current or drag-cup drive devices having a cominon drive rotor (the rotor With input shaft 1 driven in rotation from any source of power, then if winding 15 be energized to establish an eddy-current driving link from drive rotor 5 to driven rotor 12, the output shaft 2 will be rotated in an opposite direction relative to the rotation of shaft 1; yet if winding 16 is energized in place of winding 15, so as1to establish a driving link from drive rotor 5' to driven rotor 13, then the output shaft 2 will be rotated in the same direction as the rotation of shaft 1. In this manner the rotation of output shaft 2 may be instantly reversed without having to reverse the rotation of the motor powering the input shaft 1, simply by throwing a suitable switch (not shown) whereby a suitable energizing circuit for the selected one of the two windings 15 and 16 is completed. Moreover, if means are provided for varying the energizing current of each winding from zero to a maximum value, the driven shaft 2 may be driven at any desired velocity over a range extending from a maximum velocity in one direction to a maximum velocity in the opposite direction, for any given load torque.

Further, if both windings 15 and 16 are simultaneously energized, the output shaft 2 will thereby be retarded, the braking torque thus produced depending on the relative values of the energizing currents supplied to the two windings.

It will be understood that various modifications may be made in the details of construction illustrated and described without exceeding the scope of the invention. Thus, the system may readily be so devised that the driven shaft is positioned coaxially with the drive shaft. The particular number of gears in each of the two gear trains may differ from that shown. The drive ratios through said gear trains may not necessarily be opposite in sign but might possess different values of similar sign so that the selective energization of the windings 15 and 16 would then serve to provide two different ranges of speed variation in the same direction rather than in opposite directions as shown herein; however, the construction wherein said drive ratios are of opposite sign, so as to provide for the drive-reversal feature disclosed herein, constitutes a preferred embodiment of the invention. Furthermore, any suitable control circuits and switching means may be associated with the windings 15 and 16, depending on the particular application to which the device of the invention is to be put, as will be readily apparent to those familiar with the art.

What we claim is:

1. An electromagnetic coupling comprising a substantially cylindrical rotatable driving member of ferromagnetic material, a stationary member coaxial with said driving member and provided with a pair of axially spaced windings facing different portions of said driving member, a pair of ferromagnetic driven elements coaxial with said driving member and rotatable independently thereof, said driven elements being interposed between said windings, respectively, and said driving member whereby energization of either of said windings causes magnetic flux to penetrate the respective driven element and the corresponding portion of said driving member, a rotatable output element, first and second transmission means of different transmission ratios respectively linking said output element with said driven elements, and switch means for selectively energizing said windings, thereby causing entrainment of the respective driven element by said driving member.

2. An electromagnetic coupling comprising a substantially cylindrical rotatable driving member of ferromagnetic material, a stationary member coaxial with said driving member and provided with a pair of axially spaced windings facing different portions of said driving member, a pair of ferromagnetic driven elements coaxial with said driving member and rotatable independently thereof, said driven elements being interposed between said windings, respectively, and said. driving member whereby energization of either of said windings causes magnetic flux to penetrate the respective driven element and the corresponding portion of said driving member, a rotatable out. put element, and first and second transmission means respectively linking said output element with said driven elements, said transmission means being effective in opposite senses of rotation.

3. An electromagnetic coupling comprising a substantially cylindrical rotatable driving member of ferromagnetic material, a stationary member coaxially surrounding said driving member and provided with a pair of axially spaced windings facing different portions of said driving member, a pair of ferromagnetic driven elements coaxial with said driving member and rotatable independently thereof, said driven elements being interposed between said windings, respectively, and said driving member whereby energization of either of said windings causes magnetic flux to penetrate the respective driven element and the corresponding portion of said driving member, a rotatable output element, and first and second transmission means of different transmission ratios respectively linking said output element with said driven elements.

4. An electromagnetic coupling comprising a substantially cylindrical rotatable driving member of ferromagnetic material, a stationary member coaxial with said driving member and provided with a pair of axially spaced windings facing difierent portions of said driving member, a pair of ferromagnetic driven elements coaxial with said driving member and rotatable independently thereof, said driven elements being interposed between said windings, respectively, and said driving member whereby energization of either of said windings causes magnetic flux to penetrate the respective driven element and the corresponding portion of said driving member, a rotatable output element, and first and second gear trains of different transmission ratios respectively linking said output element with said driven elements.

References Cited in the file of this patent UNITED STATES PATENTS 744,423 Steckel Nov. 17, 1903 2,428,104 Winther Sept. 30, 1947 2,679,604 Jaeschke May 25, 1954 FOREIGN PATENTS 904,737 Germany Feb. 22, 1954 

